Light source apparatus and endoscope system

ABSTRACT

A fluorescent type of green light source of a semiconductor in a light source apparatus for an endoscope includes a blue excitation light source device and green emitting phosphor. The blue excitation light source device emits blue excitation light. The green emitting phosphor is excited by the blue excitation light, and emits green fluorescence. A dichroic filter in a dichroic mirror cuts off the blue excitation light from an emission spectrum of mixed light of the blue excitation light and green fluorescence from the fluorescent type of green light source. Thus, illumination light with the emission spectrum of a target can be stably supplied without influence of the blue excitation light to a light amount of blue light from a blue light source of a semiconductor.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority under 35 USC 119 from Japanese PatentApplication No. 2013-208215, filed 3 Oct. 2013, the disclosure of whichis incorporated by reference herein.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a light source apparatus and endoscopesystem in which a fluorescent type of green semiconductor light sourceis used, and illumination light of an emission spectrum of a target foruse in endoscopic imaging can be stably obtained.

2. Description Related to the Prior Art

Endoscopic imaging with an endoscope system is widely known in the fieldof medical diagnosis. The endoscope system includes an endoscope, alight source apparatus and a processing apparatus. The light sourceapparatus supplies light to the endoscope. The processing apparatusprocesses an image signal output by the endoscope. The endoscopeincludes an elongated tube for entry in a body cavity. A tip of theelongated tube has lighting windows and a viewing window. The lightingwindows apply the light to an object of interest in the body cavity. Theviewing window receives object light from the object of interest forimaging. A light guide device is incorporated in the endoscope, andincludes a fiber bundle of a plurality of optical fibers. The lightguide device guides light from the light source apparatus to thelighting windows. An image sensor is disposed behind the viewing window,for example, CCD image sensor. The object of interest illuminated withthe light is imaged by the image sensor, which outputs an image signal.The processing apparatus generates a display image of the image signal.A monitor display panel is driven to display the image, to observe theobject of interest in the body cavity.

Widely used examples of light sources in the light source apparatus area xenon lamp and halogen lamp for emitting normal white light. JP-A2007-068699 and U.S. Pat. Nos. 8,337,400 and 8,506,478 (corresponding toJP-A 2009-297290) disclose use of semiconductor light sources such aslaser diodes (LDs), light emitting diodes (LEDs) and the like for thepurpose of the endoscopic imaging.

JP-A 2007-068699 discloses the light source apparatus, in which thesemiconductor light sources have three LEDs to emit light of blue, greenand red. Components of the light of blue, green and red are combined toproduce the white light.

In the xenon lamp and halogen lamp, a ratio between light components ofblue, green and red in the white light is constant and cannot beadjusted. However, the semiconductor light sources of blue, green andred are controllable for discretely adjusting light amounts of thecolors. Illumination light of plural types can be produced easily withvarious spectra of emission.

Examples of the semiconductor light sources of green include a greensemiconductor light source having an element for emitting green lightitself, and a fluorescent type of a semiconductor light source. Thefluorescent type includes an excitation light source device for emittingexcitation light, and green emitting phosphor excited by the excitationlight for emitting green fluorescence. For example, U.S. Pat. Nos.8,337,400 and 8,506,478 disclose a fluorescent type of greensemiconductor light source having a blue excitation light source device(blue LED) and green emitting phosphor. The blue excitation light sourcedevice emits blue excitation light in a violet to blue wavelength range.The green emitting phosphor is excited by the blue excitation light foremitting green fluorescence of a green wavelength range.

Among various products of LEDs available commercially, a blue-violet LEDfor lighting in a violet to blue wavelength range is usable more widelythan a green LED for lighting in a green wavelength range, because ofsuch advantage that efficiency in the light emission of the blue-violetLED is higher than the green LED, and that its cost is lower. It isconceivable to use the fluorescent type of green semiconductor lightsource disclosed in U.S. Pat. Nos. 8,337,400 and 8,506,478 with arecently higher concern than the semiconductor light sources or greenLED for emitting green light.

Furthermore, narrow band imaging with narrow band light (special light)has been known recently in the field of the endoscopic imaging. Thenarrow band light is light of a limited wavelength range in contrastwith the white light for imaging with the entirety of a surface of bodytissue or the object of interest. In the narrow band imaging, depth ofpenetration of light into the body tissue is characteristicallydifferent between plural wavelengths. According to utilization of thischaracteristic, vessel enhancement imaging is performed to enhance partof blood vessels present in mucosa of the body tissue, as described inJP-A 2011-041758. A state of the blood vessels in abnormal tissue suchas a cancer is different from the normal tissue, so that the vesselenhancement imaging is useful for discovering an early state of a cancerin the diagnosis of cancer screening.

Examples of the semiconductor light sources disclosed in JP-A2011-041758 are a fluorescent type of white semiconductor light sourceand a green semiconductor light source. The fluorescent type of whitesemiconductor light source (white LED) emits the white light with acontinuous spectrum extending fully in a visible light wavelength range.The green semiconductor light source (green LED) emits light of a greenwavelength range of 530-550 nm. A band pass filter is disposeddownstream of the fluorescent type of white semiconductor light source,and derives light of a blue wavelength range of 390-445 nm from thewhite light. In the vessel enhancement imaging, the semiconductor lightsources are turned on, so as to apply mixed light of the green light andblue light, the green light being emitted by the green semiconductorlight source in the wavelength range of 530-550 nm, the blue light beingpassed through the band pass filter in the wavelength range of 390-445nm upon emission of the white light from the fluorescent type of whitesemiconductor light source. The blue light of this wavelength range ishighly absorbed by surface blood vessels present on the epithelium(mucosa surface). The green light of this wavelength range is highlyabsorbed by subsurface or deep blood vessels disposed deeper than thesurface blood vessels. A display image with a high contrast between theblood vessels and other tissue can be obtained.

It is conceivable to combine the structures of in JP-A 2007-068699 andU.S. Pat. Nos. 8,337,400 and 8,506,478 on the basis of the light sourceapparatus of JP-A 2011-041758 for the purpose of increasing the degreeof freedom in the spectrum of the light. According to JP-A 2007-068699,the semiconductor light sources of blue, green and red are used forperforming the vessel enhancement imaging with blue light from the bluesemiconductor light source and green light from the green semiconductorlight source. According to U.S. Pat. Nos. 8,337,400 and 8,506,478, thefluorescent type of green semiconductor light source is used for thegreen light source. However, the combined construction of the lightsource apparatus has a drawback in that illumination light of anemission spectrum cannot be stably obtained as a target of the vesselenhancement imaging. In relation to the fluorescent type of greensemiconductor light source, the blue excitation light is largelyabsorbed by the green emitting phosphor. However, part of the blueexcitation light is not absorbed by the green emitting phosphor, butpasses the green emitting phosphor and becomes emitted to the object ofinterest together with the green fluorescence. Changing the light amountof the green light may change a light amount of the blue excitationlight. As a wavelength range of the blue excitation light is overlappedon a wavelength range of blue light emitted by the blue semiconductorlight source, the light amount of the blue light is influenced by thechange in the light amount of the green light.

In the endoscopic imaging, light amounts of light of blue, green and redare controlled at a desired ratio in compliance with the purpose of theimaging, to output illumination light of a target spectrum. Assumingthat color balance of a display image is changed typically in the vesselenhancement imaging by a change in the emission spectrum of theillumination light, a serious problem arises in incorrectness in theendoscopic imaging. It is highly important to stabilize the output ofthe illumination light of the target spectrum. Also, exposure control inthe imaging is performed. In case the exposure amount of the entirety ofthe image is too low (underexposure), the light amount of theillumination light is raised. In case the exposure amount of theentirety of the image is too high (overexposure), the light amount ofthe illumination light is lowered.

In the exposure control for generating light of a spectrum as a targetfor a predetermined ratio between light amounts of the colors, it isnecessary to increase or decrease the total of the light amounts withoutchanging the spectrum of the light. However, in the use of thefluorescent type of green semiconductor light source, changing the lightamount of the green fluorescence by increasing the output of thefluorescent type of green semiconductor light source may influence tothe light amount of the blue light with the overlap of the wavelengthrange on that of the blue excitation light. Thus, the spectrum will bechanged in an unwanted manner. For those reasons, it is impossiblestably to produce illumination light of the spectrum of the target inthe use of the fluorescent type of green semiconductor light source.There is no known solution of this problem. It is conceivable toconsider an amount of the change in the blue excitation light accordingto the change in the light amount of the green fluorescence, and toadjust the light amount of the blue light with the overlap of thewavelength range with the blue excitation light by use of the amount ofthe change. However, control of lighting for this conception will bevery complicated and cannot be utilized practically.

In the patent documents indicated above, there is no description on theproblem of difficulty in stably obtaining illumination light with aspectrum of a target in use of the fluorescent type of greensemiconductor light source of the vessel enhancement imaging. Nosolution of this problem is known in the field of the endoscopicimaging.

SUMMARY OF THE INVENTION

In view of the foregoing problems, an object of the present invention isto provide a light source apparatus and endoscope system in which afluorescent type of green semiconductor light source is used, andillumination light of an emission spectrum of a target for use inendoscopic imaging can be stably obtained.

In order to achieve the above and other objects and advantages of thisinvention, a light source apparatus for supplying a light guide deviceof an endoscope with light includes a blue semiconductor light sourcefor emitting blue light of a blue wavelength range. A fluorescent typeof a green semiconductor light source has a blue excitation light sourcedevice and green emitting phosphor, the blue excitation light sourcedevice emitting blue excitation light of a violet to blue wavelengthrange overlapping on the blue wavelength range of the blue light, thegreen emitting phosphor being excited by the blue excitation light foremitting green fluorescence of a green wavelength range. A wavelengthcut-off filter component is disposed between the blue excitation lightsource device and the light guide device, for cutting off the blueexcitation light.

Preferably, furthermore, a path coupler couples two light paths from theblue and green semiconductor light sources together.

Preferably, the wavelength cut-off filter component is disposed on thepath coupler, or disposed between the path coupler and the greensemiconductor light source.

Preferably, the path coupler includes optics disposed at an intersectionpoint between the two light paths. The wavelength cut-off filtercomponent is a dichroic filter formed on the optics.

Preferably, furthermore, a driver simultaneously drives the blue andgreen semiconductor light sources for vessel enhancement imaging, tooutput mixed light of the blue light and the green fluorescence.

Preferably, furthermore, a driver alternately drives the blue and greensemiconductor light sources for vessel enhancement imaging, sequentiallyto output the blue light and the green fluorescence.

Preferably, furthermore, a driver is connected to the blue and greensemiconductor light sources, and changeable between simultaneouslighting and field sequential lighting. In the simultaneous lighting,the driver simultaneously drives the blue and green semiconductor lightsources for vessel enhancement imaging, to output mixed light of theblue light and the green fluorescence. In the field sequential lighting,the driver alternately drives the blue and green semiconductor lightsources for vessel enhancement imaging, sequentially to output the bluelight and the green fluorescence.

Preferably, the blue semiconductor light source emits the blue lightwith a peak wavelength of at least one of 405, 415, 430 and 460 nm.

Preferably, furthermore, a measurement sensor measures a light amount ofthe blue light or the green fluorescence emitted by at least one of theblue and green semiconductor light sources. An optical path deviceguides part of the blue light or the green fluorescence to themeasurement sensor. A light source controller controls power supplied tothe blue or green semiconductor light source according to a measurementresult of the measurement sensor.

Preferably, the measurement sensor and the optical path device areassociated with the green semiconductor light source, and the lightsource controller adjusts the power supplied to the blue excitationlight source device according to the measurement result.

Preferably, furthermore, a band pass filter is disposed upstream of themeasurement sensor, for receiving light emitted by the greensemiconductor light source and reflected by the optical path device, andcutting off light with a wavelength different from the green wavelengthrange of the green fluorescence.

In another preferred embodiment, the wavelength cut-off filter componentis a wavelength cut-off filter of a plate shape disposed between thegreen semiconductor light source and the optical path device.

Preferably, the optical path device includes a transparent glass plate,disposed downstream of the blue or green semiconductor light source, forreflecting the part of the blue light or the green fluorescence byFresnel reflection, to guide the part to the sensor.

Preferably, furthermore, a rotatable disk has the green emittingphosphor formed on a surface thereof. The blue excitation light sourcedevice emits the blue excitation light toward the rotatable disk beingrotated at an eccentric point thereof.

Also, an endoscope system is provided, including an endoscope having alight guide device for guiding light, and a light source apparatus forsupplying the light guide device with the light. The light sourceapparatus includes a blue semiconductor light source for emitting bluelight of a blue wavelength range. A fluorescent type of a greensemiconductor light source has a blue excitation light source device andgreen emitting phosphor, the blue excitation light source deviceemitting blue excitation light of a violet to blue wavelength rangeoverlapping on the blue wavelength range of the blue light, the greenemitting phosphor being excited by the blue excitation light foremitting green fluorescence of a green wavelength range. A wavelengthcut-off filter component is disposed between the blue excitation lightsource device and the light guide device, for cutting off the blueexcitation light.

Consequently, illumination light of an emission spectrum of a target foruse in endoscopic imaging can be stably obtained, because the wavelengthcut-off filter component cuts off a part of the blue excitation lighttraveling in an unwanted manner.

BRIEF DESCRIPTION OF THE DRAWINGS

The above objects and advantages of the present invention will becomemore apparent from the following detailed description when read inconnection with the accompanying drawings, in which:

FIG. 1 is an explanatory view in a perspective illustrating an endoscopesystem;

FIG. 2 is a front elevation illustrating a tip of an endoscope;

FIG. 3 is a block diagram schematically illustrating the endoscopesystem;

FIG. 4 is a cross section illustrating a blue semiconductor lightsource;

FIG. 5 is a cross section illustrating a green semiconductor lightsource;

FIG. 6 is a graph illustrating a spectrum of light from the blue lightsource;

FIG. 7 is a graph illustrating a spectrum of light from a redsemiconductor light source;

FIG. 8 is a graph illustrating spectra of blue excitation light andgreen fluorescence of the green light source;

FIG. 9 is a graph illustrating an absorption spectrum of hemoglobin;

FIG. 10 is a graph illustrating a scattering coefficient of body tissue;

FIG. 11 is a graph illustrating a spectrum of illumination lightcontaining the blue light, green fluorescence and red light;

FIG. 12 is a graph illustrating a spectrum of illumination lightcontaining the blue light and green fluorescence;

FIG. 13 is a graph illustrating a spectral characteristic of micro colorfilters;

FIG. 14 is a timing chart illustrating lighting and imaging according tonormal imaging;

FIG. 15 is a timing chart illustrating lighting and imaging according tovessel enhancement imaging;

FIG. 16 is a flow chart illustrating image processing in the normalimaging;

FIG. 17 is a flow chart illustrating image processing in the vesselenhancement imaging;

FIG. 18 is an explanatory view in a side elevation illustrating thelight sources and a path coupler;

FIG. 19 is a graph illustrating a transmission characteristic of adichroic filter in a first dichroic mirror;

FIG. 20 is a graph illustrating a transmission characteristic of adichroic filter in a second dichroic mirror;

FIG. 21 is an explanatory view in a side elevation illustrating a secondpreferred embodiment in which a first dichroic mirror is disposed in apath coupler;

FIG. 22 is a graph illustrating a transmission characteristic of thedichroic filter in the first dichroic mirror;

FIG. 23 is an explanatory view in a side elevation illustrating a thirdpreferred embodiment with a wavelength cut-off filter;

FIG. 24 is a graph illustrating a transmission characteristic of thewavelength cut-off filter;

FIG. 25 is an explanatory view in a side elevation illustrating a fourthpreferred embodiment with measurement sensors for light amounts;

FIGS. 26 and 27 are graphs illustrating transmission characteristics offilters disposed upstream of the green and red measurement sensors;

FIG. 28 is a block diagram schematically illustrating light amountcontrol with the measurement sensors;

FIG. 29 is an explanatory view in a side elevation illustrating a pathcoupler having the measurement sensors;

FIG. 30 is an explanatory view in a side elevation illustrating a fifthpreferred embodiment having first and second blue semiconductor lightsources;

FIGS. 31 and 32 are graphs illustrating spectra of first and second bluelight from the first and second blue light sources;

FIG. 33 is a graph illustrating a spectrum of white light;

FIGS. 34 and 35 are graphs illustrating spectra of illumination lightcontaining the first and second blue light and the green fluorescence;

FIG. 36 is a graph illustrating a transmission characteristic of adichroic filter in a third dichroic mirror;

FIG. 37 is a timing chart illustrating lighting and imaging according tothe normal imaging;

FIGS. 38 and 39 are timing charts illustrating lighting and imagingaccording to the vessel enhancement imaging of mucosal blood vessels andaccording to the vessel enhancement imaging of subsurface blood vessels;

FIG. 40 is a graph illustrating a transmission characteristic of awavelength cut-off filter;

FIG. 41 is a perspective view illustrating a sixth preferred embodimentwith a green semiconductor light source;

FIG. 42 is a timing chart illustrating lighting and imaging according tothe vessel enhancement imaging and field sequential lighting.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT(S) OF THE PRESENTINVENTION

In FIG. 1, an endoscope system 10 includes an endoscope 11, a processingapparatus 12, a light source apparatus 13 and a monitor display panel14. The endoscope 11 images an object of interest or body tissue. Theprocessing apparatus 12 receives an image signal from the endoscope 11and produces an image of the object of interest. The light sourceapparatus 13 supplies light of illumination to the endoscope 11. Thedisplay panel 14 displays the image from the processing apparatus 12. Auser input interface 15 is connected to the processing apparatus 12,inclusive of a keyboard, mouse and other input devices.

The endoscope system 10 is changeable between a normal imaging mode forimaging an object of interest, and a vessel enhancement imaging mode forenhancing and imaging blood vessels present in mucosa as object ofinterest. In the vessel enhancement imaging mode, a pattern of bloodvessels is recorded as blood vessel information, for use in diagnosis ofa benign or malignant tumor. In the vessel enhancement imaging mode, theobject of interest is illuminated with light containing components of aparticular wavelength range having a high absorption coefficient inrelation to hemoglobin in blood. In the normal imaging mode, a normalmulti-color image is produced with suitability for general diagnosis ofthe object of interest. In the vessel enhancement imaging mode, a vesselenhancement image is produced with suitability for diagnosing thepattern of blood vessels.

The endoscope 11 includes an elongated tube 16, a grip handle 17 and auniversal cable 18. The elongated tube 16 is entered in a body cavity ofa patient, for example, gastrointestinal tract. The grip handle 17 isdisposed at a proximal end of the elongated tube 16. The universal cable18 connects the endoscope 11 to the processing apparatus 12 and thelight source apparatus 13.

The elongated tube 16 includes a tip device 19, a steering device 20 anda flexible device 21 arranged in a proximal direction. In FIG. 2,various elements are disposed on an end surface of the tip device 19,including lighting windows 22, a viewing window 23, a nozzle spout 24for washing fluid, and a distal instrument opening 25. The lightingwindows 22 apply illumination light to an object of interest. Theviewing window 23 receives image light from the object of interest. Thenozzle spout 24 supplies air or water to clean up the viewing window 23.The distal instrument opening 25 is used to protrude a medicalinstrument such as a forceps, electrocautery device and the like fortreatment of various types. An image sensor 56 and an objective lens 60are disposed behind the viewing window 23. See FIG. 3.

The steering device 20 is constituted by a plurality of link elementsconnected serially. Steering wheels 26 are disposed on the grip handle17, and rotated to bend the steering device 20 up and down and to theright and left. The tip device 19 is directed in a desired direction bysteering of the steering device 20. The flexible device 21 is flexiblefor entry in a body cavity of a tortuous shape, for example, esophagusor intestines in a gastrointestinal tract. A communication cable, alight guide device 55 and the like are extended through the elongatedtube 16 as illustrated in FIG. 3. The communication cable transmits adrive signal for driving the image sensor 56, and an image signal outputby the image sensor 56. The light guide device 55 transmits light fromthe light source apparatus 13 to the lighting windows 22.

The grip handle 17 includes a proximal instrument opening 27, fluidsupply buttons 28 and a release button (not shown) in addition to thesteering wheels 26. The proximal instrument opening 27 receives entry ofa medical instrument for treatment. The fluid supply buttons 28 aredepressed for supplying air or water through the nozzle spout 24. Therelease button is depressible for forming a still image.

A tube for the universal cable 18 contains the communication cable, thelight guide device 55 and the like extending from the elongated tube 16.A composite connector 29 is disposed at a proximal end of the universalcable 18 on a side of the processing apparatus 12 and the light sourceapparatus 13. The composite connector 29 includes a cable connector plug29 a and a light source connector plug 29 b. Those are coupled torespectively the processing apparatus 12 and the light source apparatus13 in a removable manner. A proximal end of the communication cable iscontained in the cable connector plug 29 a. An entrance end 55 a of thelight guide device 55 of FIG. 3 is contained in the light sourceconnector plug 29 b.

In FIG. 3, the light source apparatus 13 includes a light source unit40, a path coupler 41 and a light source controller 42. The light sourceunit 40 includes a blue light source 35, a fluorescent type of greenlight source 36 and a red light source 37 as semiconductor lightsources. The path coupler 41 couples light paths of the B, G and R lightsources 35-37 together. The light source controller 42 controls the B, Gand R light sources 35-37.

The blue light source 35 includes a blue LED 43 (light emitting diode)for emitting light of a blue wavelength range. The red light source 37includes a red LED 45 (light emitting diode) for emitting light of a redwavelength range. Furthermore, the green light source 36 includes a blueexcitation light source device 44 or light source LED (light emittingdiode), and green emitting phosphor 47. The blue excitation light sourcedevice 44 emits blue excitation light of a violet to blue wavelengthrange. The green emitting phosphor 47 is excited by the blue excitationlight, and emits green fluorescence of a green wavelength range.

Each of the LEDs 43-45 has a p-type semiconductor and an n-typesemiconductor attached together as is well-known in the art. Uponapplication of voltage, recombination of a positive hole and an electronoccurs across the band gap at the p-n junction, for a current to flow.Light is emitted by generation of energy according to the band gap. Alight amount emitted by the LEDs 43-45 is increased by an increase insupplied power. In the green light source 36 as a combination of theblue excitation light source device 44 and the green emitting phosphor47, a light amount of the green fluorescence is increased by an increasein a light amount of the blue excitation light from the blue excitationlight source device 44.

In FIG. 4, the blue light source 35 includes a semiconductor substrate35 a or semiconductor die, a cavity mold 35 b and resin encapsulant 35c. On the semiconductor substrate 35 a, the blue LED 43 is mounted. Thecavity mold 35 b is formed in the semiconductor substrate 35 a, and hasa cavity for containing the blue LED 43. The resin encapsulant 35 c isfilled in the cavity for encapsulation. An inner surface of the cavityis a reflector for reflecting light. Light diffusing material is mixedwith and dispersed in the semiconductor substrate 35 a for diffusinglight. An LED wire 35 d extends from the blue LED 43 to thesemiconductor substrate 35 a for connection with conductivity. In thetechnical field of the LED, this type of mounting of the blue lightsource 35 is referred to as a surface mounting type. Note that, in thered light source 37, the structure of the blue light source 35 isrepeated. Details of the red light source 37 are not described herein.

In FIG. 5, the green light source 36 of the fluorescent type includes asemiconductor substrate 36 a or semiconductor die, and a cavity mold 36b, and is packaged with the blue excitation light source device 44 inthe surface mounting type, in a manner similar to the blue and red lightsources 35 and 37. The green light source 36 is different from the blueand red light sources 35 and 37 in that the green emitting phosphor 47is contained in the cavity of the cavity mold 36 b. The green emittingphosphor 47 in the blue excitation light source device 44 is dispersedin resin encapsulant, and includes dispersed materials such as phosphor,light diffusing material and the like. An LED wire 36 d is disposed toconnect the semiconductor substrate 36 a to the blue excitation lightsource device 44.

In FIG. 6, the blue LED 43 emits blue light LB of which a wavelengthrange is 390-445 nm of violet to blue colors, and a peak wavelength is430 plus or minus 10 nm. In FIG. 7, the red LED 45 emits red light LR ofwhich a wavelength range is 615-635 nm of a red color, and a peakwavelength is 620 plus or minus 10 nm.

In FIG. 8, the green light source 36 emits mixed light (LBe+LGf) of blueexcitation light LBe from the blue excitation light source device 44 andgreen fluorescence LGf emitted by the green emitting phosphor 47 excitedby the blue excitation light LBe. The blue excitation light LBe has aviolet to blue wavelength range of 420-440 nm and a peak wavelength of430 plus or minus 10 nm. The green fluorescence LGf has a greenwavelength range of 500-600 nm and a peak wavelength of 520 plus orminus 10 nm. The peak wavelength of the blue excitation light LBe isequal to that of the blue light LB emitted by the blue light source 35.The wavelength range of the blue excitation light LBe is overlapped withthat of the blue light LB. See FIG. 19.

The green emitting phosphor 47 absorbs a large part of the blueexcitation light LBe to emit the green fluorescence LGf. A remainingpart of the blue excitation light LBe passes the green emitting phosphor47 without absorption. A spectrum of light emitted by the green lightsource 36, as illustrated in the drawing, contains a component of thepassed part of the blue excitation light LBe through the green emittingphosphor 47 and a component of the green fluorescence LGf.

In FIG. 9, an absorption spectrum of hemoglobin in blood is illustrated.An absorption coefficient μa has dependency to the wavelength, namelyincreases abruptly in a wavelength range equal to or lower than 450 nm,and comes to a peak at approximately 405 nm. Also, the absorptioncoefficient comes to a smaller peak at a wavelength of 530-560 nm. Incase light of a wavelength range with a high value of the absorptioncoefficient μa is applied to body tissue or an object of interest, animage with a difference in the contrast between blood vessels and othertissue can be obtained, because the light is largely absorbed by theblood vessels.

In FIG. 10, a scattering characteristic of body tissue to light also hasdependency to the wavelength. A scattering coefficient μS increasesaccording to smallness of the wavelength. The scattering influences adepth of penetration of light into the body tissue. An amount of lightreflected in the vicinity of the epithelium (mucosa surface) of the bodytissue is high according to highness of the scattering, so as todecrease an amount of light reaching a portion of a medium depth orlarge depth (lamina propria or muscularis mucosae). Accordingly, thedepth of penetration decreases according to the smallness of thewavelength, and increases according to greatness of the wavelength. Awavelength of light for the vessel enhancement is selected according tothe absorption characteristic of hemoglobin and scatteringcharacteristic of body tissue to light.

The blue light LB with the peak wavelength of 430 plus or minus 10 nmfrom the blue LED 43 has a relatively small depth of penetration with arelatively short wavelength. Absorption of the blue light LB in surfaceblood vessels is large. Thus, the blue light LB is used for enhancementof surface blood vessels. It is possible to obtain a vessel enhancementimage in which surface blood vessels are expressed with high contrast byuse of the blue light LB. Also, green fluorescence LGf with the peakwavelength of 520 plus or minus 10 nm is used for enhancement ofsubsurface or deep blood vessels. In FIG. 9 for the absorption spectrum,the absorption coefficient changes gradually in a green wavelength rangeof 530-560 nm in comparison with a blue wavelength range equal to orless than 450 nm. There is no requirement of narrow band light for thepurpose of enhancement of subsurface or deep blood vessels in a mannerdifferent from the blue light LB. Thus, a green image signal after colorseparation with a micro color filter of green in the image sensor 56 isused for enhancement of the subsurface or deep blood vessels, as will bedescribed later.

In FIG. 3, drivers 50, 51 and 52 are connected to respectively the LEDs43-45. The light source controller 42 controls the drivers 50-52 to turnon and off the LEDs 43-45 and adjust their light amounts. According toan exposure control signal from the processing apparatus 12, the lightsource controller 42 adjusts the light amounts by changing powersupplied to the LEDs 43-45.

The drivers 50-52 are controlled by the light source controller 42, andturn on respectively the LEDs 43-45 by application of drive currents. Inresponse to the exposure control signal from the processing apparatus12, the drivers 50-52 change the current values to adjust power for theLEDs 43-45, so that light amounts of the blue light LB, greenfluorescence LGf and red light LR are controlled. Control of the lightamount of the green fluorescence LGf is performed by controlling a lightamount of the blue excitation light LBe from the blue excitation lightsource device 44. In case an operator wishes an increase of the lightamount of the green fluorescence LGf, the current value from the driver51 to the blue excitation light source device 44 is increased toincrease the light amount of the blue excitation light LBe. Note thatvarious methods of supplying a drive current can be used, such ascontrols of PAM (pulse amplitude modulation) and PWM (pulse widthmodulation). In the PAM, an amplitude of a pulse of the drive current ischanged. In the PWM, a duty factor of the pulse of the drive current ischanged.

The path coupler 41 couples light paths of light from the B, G and Rlight sources 35-37 together into one light path. There is a receptacleconnector 54 for connection of the light source connector plug 29 b. Adistal end of the path coupler 41 is disposed near to the receptacleconnector 54. The path coupler 41 receives the light from the B, G and Rlight sources 35-37 and outputs the light toward the entrance end 55 aof the light guide device 55 in the endoscope 11. Protectors (not shown)of glass are associated with respectively the light source connectorplug 29 b and the receptacle connector 54.

In FIG. 11, a spectrum of mixed light of the blue light LB, greenfluorescence LGf and red light LR from the B, G and R light sources35-37 at a point downstream of the path coupler 41 is illustrated. Themixed light is white light with the continuous spectrum fully extendingin a visible light range, and used as illumination light LW0 in thenormal imaging mode. In the vessel enhancement imaging mode,illumination light LW1 is applied to an object of interest as mixedlight of the blue light LB and green fluorescence LGf. See FIG. 12. Asecond dichroic mirror 80 of FIG. 18 cuts off the blue excitation lightLBe, so that no component of the blue excitation light LBe is containedin a spectrum of the illumination light LW0 and LW1. Note that thespectra of the illumination light LW0 and LW1 in FIGS. 11 and 12 areonly examples. Spectra of the illumination light LW0 and LW1 can bechanged suitably as target according to color balance of a display imageor the like. For example, a ratio between light amounts of the bluelight LB, green fluorescence LGf and red light LR (ratio between currentvalues of drive currents for the LEDs 43-45) is adjusted to produce theillumination light LW0 and LW1 with a spectrum of the target.

The light source controller 42 controls the exposure of the light ofillumination by maintaining the spectrum of light emission as a target.Should a ratio of light amounts of the colors be changed within thelight of illumination, color balance of a display image may change witha change in the spectrum of the light emission. Thus, the light sourcecontroller 42 discretely changes a current value of driving the LEDs43-45 by controlling the drivers 50-52, to increase or decrease thelight amounts of the colors.

The light source controller 42 changes the spectrum of light between thenormal imaging mode and the vessel enhancement imaging mode. Forexample, the light source controller 42 sets the ratio of the lightamount of the blue light LB higher in the vessel enhancement imagingmode than in the normal imaging mode, so as to use the blue light LBwith higher importance than the green fluorescence LGf.

In FIG. 3, the endoscope 11 includes the light guide device 55, theimage sensor 56, an analog processing unit 57 or analog front end (AFE),and an imaging control unit 58. The light guide device 55 is a fiberbundle constituted by bundling plural optical fibers. Upon coupling thelight source connector plug 29 b to the light source apparatus 13, theentrance end 55 a of the light guide device 55 in the light sourceconnector plug 29 b is aligned with an exit end of the path coupler 41.A distal exit end of the light guide device 55 inside the tip device 19has two branches for transmitting light to the lighting windows 22.

A lighting lens 59 is disposed behind each of the lighting windows 22.Illumination light from the light source apparatus 13 is guided by thelight guide device 55 to the lighting lens 59, and applied through thelighting windows 22 to an object of interest. The lighting lens 59 is aconcave lens and enlarges a divergence angle of light from the lightguide device 55. The illumination light can be applied to a wide area ina body cavity with the object of interest.

The objective lens 60 and the image sensor 56 are disposed behind theviewing window 23. Image light from the object of interest enters theobjective lens 60 through the viewing window 23, and is focused on animaging surface 56 a of the image sensor 56 by the objective lens 60.

Examples of the image sensor 56 are a CCD image sensor and CMOS imagesensor. A plurality of photoconductive elements or photoconductors arearranged as pixels of arrays on the imaging surface 56 a, for example,photo diodes. The image sensor 56 photoelectrically converts lightreceived by the imaging surface 56 a, and stores signal charge accordingto light amounts of light received by the pixels. The signal charge isconverted by an amplifier into a voltage signal, which is read out. Thevoltage signal is transmitted by the image sensor 56 to the analogprocessing unit 57 as an image signal.

The analog processing unit 57 is constituted by a correlated doublesampler (CDS), auto gain controller (AGC) and A/D converter (all notshown). The correlated double sampler processes the image signal of ananalog form from the image sensor 56 in the correlated double sampling,and removes electric noise due to reset of the signal charge. The autogain controller amplifies the image signal after removal of the noise inthe correlated double sampler. The A/D converter converts the amplifiedimage signal from the auto gain controller into a digital image signalhaving a gradation value according to a predetermined bit number, andsends the digital image signal to the processing apparatus 12.

A controller 65 in the processing apparatus 12 is connected with theimaging control unit 58, which supplies the image sensor 56 with a drivesignal according to a clock signal from the controller 65 as areference. The image sensor 56 generates an image signal at apredetermined frame rate according to the drive signal from the imagingcontrol unit 58, and sends the image signal to the analog processingunit 57.

The image sensor 56 is a color image sensor. The imaging surface 56 a ofthe image sensor 56 has a great number of micro color filters of blue,green and red with spectral characteristics in FIG. 13 in correspondencewith pixels. An example of arrangement of the micro color filters is aBayer arrangement.

The B pixels with the B filters are sensitive to light of a wavelengthof approximately 380-560 nm. The G pixels with the G filters aresensitive to light of a wavelength of approximately 450-630 nm. The Rpixels with the R filters are sensitive to light of a wavelength ofapproximately 580-800 nm. Reflected light corresponding to the bluelight LB is mainly received by the B pixels. Reflected lightcorresponding to the green fluorescence LGf is mainly received by the Gpixels. Reflected light corresponding to the red light LR is mainlyreceived by the R pixels. The blue excitation light LBe does not travelto the object of interest because cut off by the second dichroic mirror80. Assuming that the blue excitation light LBe illuminates the object,reflected light from the object is sensed by the B pixels.

In FIGS. 14 and 15, the image sensor 56 operates for the storing andreadout in a period of acquiring one frame, and in the storing, storessignal charge in pixels, and in the readout, reads out the stored signalcharge. In FIG. 14, the B, G and R light sources 35-37 in the normalimaging mode are turned on according to a time point of the storing ofthe image sensor 56, to apply the illumination light LW0 (LB+LGf+LR) toan object of interest, the illumination light LW0 being mixture of theblue light LB, green fluorescence LGf and red light LR. Object light orreflected light becomes incident upon the image sensor 56. The imagesensor 56 separates the reflected light of the illumination light LW0with the micro color filter. Blue pixels receive reflected light derivedfrom the blue light LB. Green pixels receive reflected light derivedfrom the green fluorescence LGf. Red pixels receive reflected lightderived from the red light LR. The image sensor 56 sequentially outputsimage signals B, G and R of one frame according to pixel values of theblue, green and red pixels at a time point of the readout and with theframe rate. The imaging sequence is repeated while the normal imagingmode is set.

In FIG. 15, the blue and green light sources 35 and 36 in the vesselenhancement imaging mode are turned on according to a time point of thestoring of the image sensor 56, to apply illumination light LW1 (LB+LGf)to the object of interest, the illumination light LW1 being mixture ofthe blue light LB and green fluorescence LGf.

The illumination light LW1 is separated by the micro color filters inthe image sensor 56 in a manner similar to the normal imaging mode. TheB and G pixels receive reflected light derived from the blue light LBand from the green fluorescence LGf in a manner similar to the normalimaging mode. The image sensor 56 outputs image signals B, G and Rsequentially in a sequence of readout in the vessel enhancement imagingmode. Those steps of the imaging are repeated while the vesselenhancement imaging mode is set.

In FIG. 3, the processing apparatus 12 includes a digital signalprocessor 66 (DSP), an image processing unit 67, a frame memory 68 and adisplay control unit 69 together with the controller 65. The controller65 has a CPU with a ROM and a RAM. The ROM stores control programs andcontrol data. The RAM is a working memory for loading of the controlprograms. The CPU runs the control programs to control various elementsin the processing apparatus 12.

The digital signal processor 66 acquires an image signal output by theimage sensor 56. The digital signal processor 66 separates the imagesignal of the mixture for blue, green and red pixels into image signalsof blue, green and red. The image signals of the colors are interpolatedin the operation of pixel interpolation. The digital signal processor 66performs signal processing of various functions, such as gammacorrection, white balance correction and the like for the image signalsof blue, green and red.

The digital signal processor 66 determines an exposure amount accordingto the image signals B, G and R. Should the exposure amount of theentirety of the image be too low (underexposure), the digital signalprocessor 66 outputs a control signal to the controller 65 to raise thelight amount of the illumination light. Should the exposure amount ofthe entirety of the image be too high (overexposure), the digital signalprocessor 66 outputs a control signal to the controller 65 to lower thelight amount of the illumination light. The controller 65 sends thecontrol signal to the light source controller 42 of the light sourceapparatus 13.

The frame memory 68 stores image data output by the digital signalprocessor 66, processed image data from the image processing unit 67,and the like. The display control unit 69 reads out the processed imagedata from the frame memory 68, converts this into a video signal such asa composite signal, component signal or the like, which is output to thedisplay panel 14.

In FIG. 16, the image processing unit 67 in the normal imaging modegenerates a normal image according to the image signals B, G and R aftercolor separation by the digital signal processor 66. The normal image isoutput to the display panel 14. The image processing unit 67 updates thenormal image at each time that the image signals B, G and R in the framememory 68 are updated.

In FIG. 17, the image processing unit 67 generates a vessel enhancementimage according to image signals B and G in the vessel enhancementimaging mode. The image signal B in the vessel enhancement imaging modeincludes a component of reflected light derived from the blue light LBhaving a wavelength of 390-445 nm and a peak wavelength of 430 plus orminus 10 nm. Thus, the surface blood vessels can be expressed at a highcontrast. It is medically known that there is a characteristic patternof the particular surface blood vessels in body tissue of a cancer,malignant tumor or other lesions, because higher vessel density of theparticular surface blood vessels is found than normal body tissue. It ispreferable to express the particular surface blood vessels distinctlywith advantages for the diagnosis of a benign or malignant tumor.

It is also possible to extract an area of the surface blood vesselswithin the endoscopic image according to the image signal B, and processthe area of the surface blood vessels in edge enhancement as processingwell-known in the art. The image signal B after the edge enhancement iscombined with the image signal G, to produce a vessel enhancement image.Also, an area of subsurface or deep blood vessels can be processed inthe edge enhancement in addition to the surface blood vessels. To thisend, an area of the subsurface or deep blood vessels is extracted fromthe image signal G containing much information of the subsurface or deepblood vessels, and is processed in the edge enhancement. A vesselenhancement image is produced according to the image signal G after theedge enhancement and the image signal B.

The image processing unit 67 generates the vessel enhancement image ateach time that the image signals B and G in the frame memory 68 areupdated. The display control unit 69 allocates the image signal B to theB and G channels of the display panel 14, and the image signal G to theR channel of the display panel 14, and drives the display panel 14 todisplay the vessel enhancement image in a form of pseudo color.

In FIG. 18, the path coupler 41 includes collimator lenses 75, 76 and77, a first dichroic mirror 79, the second dichroic mirror 80 and acondenser lens 82. The collimator lenses 75-77 collimate light of thecolors from respectively the B, G and R light sources 35-37. Thecondenser lens 82 condenses light from the path coupler 41 to theentrance end 55 a of the light guide device 55. Each of the first andsecond dichroic mirrors 79 and 80 is optics including a transparentglass plate and a layer of a dichroic filter formed on the glass platewith a predetermined transmission characteristic.

The green light source 36 is so disposed that its light path is alignedwith an optical axis of the light guide device 55. The light paths ofthe green and red light sources 36 and 37 are perpendicular with oneanother. The first dichroic mirror 79 is positioned at a point of theintersection between the light paths of the green and red light sources36 and 37. Also, the light paths of the blue and green light sources 35and 36 are perpendicular with one another. The second dichroic mirror 80is positioned at a point of the intersection between the light paths ofthe blue and green light sources 35 and 36. The first dichroic mirror 79is oriented with an inclination of 45 degrees with respect to the lightpaths of the green and red light sources 36 and 37. The second dichroicmirror 80 is oriented with an inclination of 45 degrees with respect tothe light paths of the blue and green light sources 35 and 36.

In FIG. 19, the dichroic filter of the first dichroic mirror 79 has atransmission characteristic of reflecting light of a red wavelengthrange equal to or more than approximately 600 nm and passing light of ablue to green wavelength range less than the same. The first dichroicmirror 79 passes the mixed light of the blue excitation light LBe andgreen fluorescence LGf from the green light source 36 through thecollimator lens 76, and reflects the red light LR from the red lightsource 37 through the collimator lens 77. Thus, a light path of themixed light of the blue excitation light LBe and green fluorescence LGfis combined with that of the red light LR for coupling.

A dichroic filter in the second dichroic mirror 80 has a transmissioncharacteristic of cutting off at least the blue excitation light LBefrom a spectrum of mixed light of the blue excitation light LBe andgreen fluorescence LGf downstream of the green light source 36 asillustrated in FIG. 8. In short, the dichroic filter in the seconddichroic mirror 80 operates as an excitation light cut-off filter(wavelength cut-off filter component) for cutting off the blueexcitation light LBe.

In FIG. 20, the dichroic filter of the second dichroic mirror 80 has atransmission characteristic of reflecting light of a violet to bluewavelength range less than approximately 460 nm and passing light of agreen to red wavelength range more than the same. The second dichroicmirror 80 reflects the blue excitation light LBe in the mixed light ofthe blue excitation light LBe and green fluorescence LGf downstream ofthe first dichroic mirror 79, and passes the green fluorescence LGf.Also, the second dichroic mirror 80 passes the red light LR reflected bythe first dichroic mirror 79, and reflects the blue light LB from theblue light source 35 through the collimator lens 75. Thus, the seconddichroic mirror 80 couples light paths of the blue excitation light LBe,green fluorescence LGf and red light LR together. Note that the blueexcitation light LBe does not enter the entrance end 55 a of the lightguide device 55, and is prevented from illuminating an object ofinterest.

The operation of the present embodiment is described now. For endoscopicimaging, the endoscope 11 is connected to the processing apparatus 12and the light source apparatus 13. A power source for the processingapparatus 12 and the light source apparatus 13 is turned on to start upthe endoscope system 10.

The elongated tube 16 of the endoscope 11 is entered in thegastrointestinal tract of the patient to start imaging. In the normalimaging mode, the B, G and R light sources 35-37 are turned on. Thelight source controller 42 sets current values for driving the LEDs43-45 at a level suitable for the normal imaging mode, and startsdriving the B, G and R light sources 35-37. The light source controller42 controls light amounts by maintaining a spectrum of emission for atarget.

In the blue and red light sources 35 and 37, the LEDs 43 and 45 emitblue light LB and red light LR. The green light source 36 of thefluorescent type emits mixed light of the blue excitation light LBe fromthe blue excitation light source device 44 and the green fluorescenceLGf from the green emitting phosphor 47 upon excitation with the blueexcitation light LBe. The components of the light enter the collimatorlenses 75-77 in the path coupler 41.

The red light LR is reflected by the first dichroic mirror 79 and passedthrough the second dichroic mirror 80. The mixed light of the blueexcitation light LBe and green fluorescence LGf is passed through thefirst dichroic mirror 79. The blue excitation light LBe is reflected bythe second dichroic mirror 80. The green fluorescence LGf is passedthrough the second dichroic mirror 80. Thus, the first dichroic mirror79 couples light paths of the red light LR, the blue excitation lightLBe and the green fluorescence LGf in mixture. The second dichroicmirror 80 cuts off the blue excitation light LBe. The dichroic filter inthe second dichroic mirror 80 operates as an excitation light cut-offfilter (wavelength cut-off filter component), so that the optical systemof the path coupler 41 can be constructed with simplicity.

The blue light LB is reflected by the second dichroic mirror 80. Thesecond dichroic mirror 80 couples the paths of the blue light LB, greenfluorescence LGf and red light LR together. The light components of theblue light LB, green fluorescence LGf and red light LR become incidentupon the condenser lens 82. Thus, illumination light LW0 is producedfrom the combination of the blue light LB, green fluorescence LGf andred light LR. The condenser lens 82 condenses the illumination light LW0at the entrance end 55 a of the light guide device 55 of the endoscope11, and supplies the endoscope 11 with the illumination light LW0.

In the endoscope 11, the illumination light LW0 is guided through thelight guide device 55 to the lighting windows 22, and applied to anobject of interest. Reflected light of the illumination light LW0 fromthe object of interest becomes incident upon the image sensor 56 throughthe viewing window 23. The image sensor 56 outputs image signals B, Gand R to the digital signal processor 66 of the processing apparatus 12.The digital signal processor 66 separates the image signals B, G and Rby color separation, and inputs those to the image processing unit 67.Imaging of the image sensor 56 is repeated at a predetermined framerate. The image processing unit 67 generates a normal image according tothe image signals B, G and R. The display control unit 69 outputs thenormal image to the display panel 14. Also, the normal image is updatedaccording to the frame rate of the image sensor 56.

The digital signal processor 66 obtains an exposure amount according tothe image signals B, G and R, and transmits an exposure control signalto the light source controller 42 of the light source apparatus 13according to the obtained exposure amount. The light source controller42 acquires current values of driving the B, G and R light sources 35-37according to the exposure control signal so as to keep a constant ratiobetween the light amounts of the colors (or not to change the spectrumof the light emission of a target). Thus, the B, G and R light sources35-37 are driven according to the acquired current values. It istherefore possible to keep the light amounts of the blue light LB, greenfluorescence LGf and red light LR from the B, G and R light sources35-37 at the constant ratio suitable for the normal imaging mode.

To change the light amount of green fluorescence LGf in the exposurecontrol, the light amount of blue excitation light LBe from the blueexcitation light source device 44 is changed. In FIG. 19, a wavelengthrange of the blue excitation light LBe overlaps on that of the bluelight LB. Assuming that the blue excitation light LBe is emitted forillumination, a light amount of the blue light LB is also changed by achange in that of the blue excitation light LBe. The spectrum of thelight is changed. However, the second dichroic mirror 80 cuts off theblue excitation light LBe, so that the light amount of the blue light LBis controlled discretely from the green fluorescence LGf withoutinfluence of the blue excitation light LBe to the light amount of theblue light LB. Consequently, the endoscope 11 can be supplied with lightof the spectrum appropriate for the normal imaging mode even uponperforming the exposure control. No change occurs in the color balanceof the normal image.

Assuming that an object with appearance of a lesion is discovered in thenormal imaging mode, the imaging mode is changed over to the vesselenhancement imaging mode. The red light source 37 is turned off, and theblue and green light sources 35 and 36 are turned on. Color light fromthe blue and green light sources 35 and 36 is combined to become theillumination light LW1 by the path coupler 41, and is supplied to theendoscope 11. In a manner similar to the normal imaging mode, the seconddichroic mirror 80 cuts off the blue excitation light LBe. Thus, theendoscope 11 can be supplied constantly with light of a spectrumsuitable for the vessel enhancement imaging mode, without change in thecolor balance of a vessel enhancement image.

The image sensor 56 receives reflected light from an object of interestilluminated by the illumination light LW1, and outputs image signals B,G and R to the digital signal processor 66. The digital signal processor66 separates the image signals B, G and R and inputs those to the imageprocessing unit 67, which generates a vessel enhancement image accordingto the image signals B and G. The vessel enhancement image is output tothe display panel 14. This image is updated according to the frame rateof the image sensor 56.

Therefore, reliability of a vessel enhancement image can be high owingto constant emission of light of a spectrum suitable of the vesselenhancement imaging. The vessel enhancement image is used for diagnosinga benign or malignant tumor. Reliability in the diagnosis of a tumor canbe high according to the highness in the reliability in the vesselenhancement image.

The blue excitation light LBe with influence to the light amount of theblue light LB is cut off by the second dichroic mirror 80. Thus, it ispossible to supply light of illumination with the spectrum of targetwithout complicated control of adjusting the light amount of the bluelight LB and the like in consideration of a change in the blueexcitation light LBe with a change in the green fluorescence LGf.

Second Preferred Embodiment

In the first embodiment, the second dichroic mirror 80 includes thedichroic filter functioning as an excitation light cut-off filter. Inthe second embodiment, a dichroic mirror separate from the seconddichroic mirror 80 has a dichroic filter functioning as an excitationlight cut-off filter (wavelength cut-off filter component).

In FIG. 21, a path coupler 90 in a light source apparatus 85 includes afirst dichroic mirror 91, which corresponds to the first dichroic mirror79 of the first embodiment, and couples a light path of mixed light ofthe blue excitation light LBe and green fluorescence LGf from the greenlight source 36 with a light path of the red light LR from the red lightsource 37. A dichroic filter in the first dichroic mirror 91 operatesalso as an excitation light cut-off filter. In the path coupler 90, thepath coupler 41 is repeated except for having the first dichroic mirror91 instead of the first dichroic mirror 79.

As illustrated in FIG. 22, the dichroic filter of the first dichroicmirror 91 is caused to have a characteristic of reflecting light of ared wavelength range equal to or more than approximately 600 nm andlight of a violet to blue wavelength range less than approximately 460nm, and passing other light of a green wavelength range. In other words,the dichroic filter comes to have the band-pass characteristic ofcombining transmission characteristics of the first and second dichroicmirrors 79 and 80 in the first embodiment. However, there is ashortcoming of a high manufacturing cost of this band-passcharacteristic in comparison with a short pass filter of transmittinglight of only a short wavelength side or a long pass filter oftransmitting light of only a long wavelength side. The structure of thefirst embodiment has an advantage in a lower cost, in that the dichroicfilter in the second dichroic mirror 80 of a long pass characteristichas a function of the excitation light cut-off filter.

Third Preferred Embodiment

In FIG. 23, another preferred light source apparatus 95 is illustrated.A path coupler 96 has a dichroic mirror and an excitation light cut-offfilter separate from the dichroic mirror. A wavelength cut-off filter 97or excitation light cut-off filter (or reduction filter) is disposedbetween the green light source 36 and the first dichroic mirror 79. InFIG. 24, the wavelength cut-off filter 97 reflects light of a violet toblue wavelength range less than approximately 460 nm, and passes lightof a green to red wavelength range other than the same. Furthermore, thewavelength cut-off filter 97 may be disposed between the first andsecond dichroic mirrors 79 and 80. In conclusion, entry of the blueexcitation light LBe to the entrance end 55 a of the light guide device55 should be prevented. An excitation light cut-off filter can bedisposed between the blue excitation light source device 44 and thelight guide device 55, and more precisely, a coupling position(intersection point) of coupling a light path of mixed light of the blueexcitation light LBe and green fluorescence LGf from the green lightsource 36 and a light path of the blue light LB from the blue lightsource 35, or a position upstream from the coupling position in thelight path.

Fourth Preferred Embodiment

In the first embodiment, the current values for the LEDs 43-45 arecontrolled. However, a light amount of a semiconductor light sourcerelative to a current value of driving may be changed by influence ofvarious factors, including heat generated by LEDs or phosphor ordegradation with time. In the fourth embodiment, measurement sensors areused for measuring light amounts of the colors, to monitor a reach ofthe light amounts of the colors to a target value according to an outputsignal from the measurement sensors.

In FIG. 25, a path coupler 100 in a light source apparatus 99 has theelements in the path coupler 41 of FIG. 18, and also includes a bluemeasurement sensor 101, a green measurement sensor 102 and a redmeasurement sensor 103 for light amounts, and glass plates 105, 106 and107. The measurement sensors 101-103 measure the light amounts of thelight of the colors from the B, G and R light sources 35-37. The glassplates 105-107 are disposed directly downstream of respectively the B, Gand R light sources 35-37, and partially reflect light from the B, G andR light sources 35-37, to guide the light toward the measurement sensors101-103.

The glass plates 105-107 are inclined with an angle of approximately 35degrees with reference to the optical axes of the B, G and R lightsources 35-37. The glass plates 105-107 pass light of the colors fromthe B, G and R light sources 35-37. There occurs Fresnel reflection uponincidence of the light on the glass plates 105-107. The glass plates105-107 (optical path devices) guide partial light (as small as 4-8%)included in the light from the B, G and R light sources 35-37 toward themeasurement sensors 101-103 by utilizing the Fresnel reflection. Also,it is possible to use other optical path devices such as optical fibersor the like, instead of the glass plates.

A band pass filter 109 and a long pass filter 110 are disposed upstreamof respectively the measurement sensors 102 and 103. The band passfilter 109 at the green measurement sensor 102 converts light into lightof a limited wavelength range of the green fluorescence LGf constitutingthe illumination light LW0 and LW1 for final supply to the endoscope 11.In FIG. 26, the band pass filter 109 has a transmission characteristicof reflecting light of a red wavelength range equal to or more thanapproximately 600 nm and light of a violet to blue wavelength range lessthan approximately 460 nm, and passing light of a green wavelength rangeother than those wavelength ranges. In short, the band pass filter 109has a band pass characteristic in combination of the transmissioncharacteristics of the first and second dichroic mirrors 79 and 80 ofthe first embodiment, in a manner similar to the first dichroic mirror91. The band pass filter 109 causes entry of the green fluorescence LGfto the green measurement sensor 102 after cutting off the blueexcitation light LBe as a partial component of the illumination lightLW0 and LW1. It is possible to measure the light amount of the greenfluorescence LGf precisely.

The long pass filter 110 at the red measurement sensor 103 convertslight into light of a limited wavelength range of the red light LRconstituting the light LW0 for final supply to the endoscope 11. In FIG.27, the long pass filter 110 has a transmission characteristic ofreflecting light of a green to blue wavelength range less thanapproximately 600 nm and passing light of a red wavelength range morethan 600 nm. In short, the transmission characteristic of the long passfilter 110 is opposite to the transmission characteristic of the firstdichroic mirror 79 of the first embodiment as illustrated in FIG. 19. Inoperation of the long pass filter 110, only the red light LR output as apart of the illumination light LW0 becomes incident upon the redmeasurement sensor 103. Thus, a light amount of the red light LR can bemeasured with precision.

In FIG. 28, the measurement sensors 101-103 receive light of the colorsguided by the glass plates 105-107 of the Fresnel reflection, and outputmeasurement signals to the light source controller 42 according to lightamounts of the colors. The light source controller 42 compares each ofthe measurement signals to a reference signal of a target light amount,and finely adjusts the current values of the drive currents for the B, Gand R light sources 35-37 according to the exposure control to set thelight amounts equal to the target light amount according to thecomparison. This is effective in constantly controlling the lightamounts by monitoring with the measurement sensors 101-103 and the fineadjustment of the current values. The light of a spectrum of the targetcan be obtained with high stability.

In FIG. 29, another preferred light source apparatus 115 is illustrated.A path coupler 116 has a wavelength cut-off filter 117 or excitationlight cut-off filter (or reduction filter) at a plate shape disposedbetween the green light source 36 and the first dichroic mirror 79 (theposition of the wavelength cut-off filter 97 of the third embodiment inFIG. 23) with the same transmission characteristic as the band passfilter 109. Thus, it is unnecessary to use the band pass filter 109.However, there is a shortcoming in that a size of the wavelength cut-offfilter 117 is larger than the band pass filter 109. The use of the bandpass filter 109 is advantageous in view of reducing a cost and saving aspace in comparison with the wavelength cut-off filter 117.

In the fourth embodiment, the measurement sensors are used for all ofthe semiconductor light sources. However, it is possible only to use themeasurement sensor for the green light source 36, but not to usemeasurement sensors for the remaining semiconductor light sources, as achange in the light amount relative to the current value is remarkablylarge in the green light source 36.

In the fourth embodiment, the measurement sensors 101-103 measure lightamounts downstream of the collimator lenses 75-77. However, the lightamounts may be measured between the collimator lenses 75-77 and the B, Gand R light sources 35-37 by use of the measurement sensors 101-103.Components of the light of the colors are diffused light, so that themeasurement sensors 101-103 can directly measure the light amounts fromthe B, G and R light sources 35-37. Thus, it is unnecessary to disposethe glass plates 105-107 as an optical path device for guiding light.

Fifth Preferred Embodiment

The blue light source 35 in the above embodiments is a single devicewith its wavelength range and peak wavelength. Another preferredembodiment has a plurality of blue light sources of which the wavelengthrange and peak wavelength are different from one another. Those lightsources are used in a distinct manner from one another by considering astate of surface blood vessels.

In FIG. 30, a light source apparatus 120 includes a light source unit123 and a path coupler 124. The light source apparatus 120 has the greenand red light sources 36 and 37, and also a first blue light source 121and a second blue light source 122 of a semiconductor. The path coupler124 couples light paths from the blue and green light sources 35 and 36and the blue light sources 121 and 122. The first blue light source 121is present in place of the blue light source 35 of the aboveembodiments. For remaining parts, the first embodiment is repeated.Elements similar to those of the above embodiments are designated withidentical reference numerals.

For the blue light sources 121 and 122, the form of the blue lightsource 35 in FIG. 4 is repeated. In FIG. 31, the first blue light source121 emits first blue light LB1 having a component of 400-470 nm as ablue wavelength range, and a peak wavelength of 460 plus or minus 10 nm.In FIG. 32, the second blue light source 122 emits second blue light LB2having a component of 395-415 nm as a violet to blue wavelength range,and a peak wavelength of 405 plus or minus 10 nm.

The path coupler 124 includes the path coupler 41, a collimator lens 125and a third dichroic mirror 126. The collimator lens 125 collimates thesecond blue light LB2 from the second blue light source 122. Thecollimator lens 125 couples light paths of the first blue light LB1 fromthe first blue light source 121 and the second blue light LB2 from thesecond blue light source 122. The path coupler 124 combines the lightpaths of the first and second blue light LB1 and LB2, green fluorescenceLGf and red light LR to form one light path. In FIG. 33, a spectrum ofthe mixed light of the first blue light LB1, green fluorescence LGf andred light LR downstream of the path coupler 124 is illustrated. Themixed light is used as the illumination light LW2 in the embodiment forthe normal imaging mode.

In FIG. 34, a spectrum of mixed light of the first blue light LB1 andgreen fluorescence LGf is illustrated. In FIG. 35, a spectrum of mixedlight of the second blue light LB2 and green fluorescence LGf isillustrated. The illumination light LW3 and LW4 is utilized in thepresent embodiment for the vessel enhancement imaging mode by way of themixed light in FIGS. 34 and 35.

The blue light sources 121 and 122 are so disposed that their lightpaths extend perpendicularly with one another. The third dichroic mirror126 is positioned at a point of the intersection of those light paths.The third dichroic mirror 126 is oriented with an inclination of 45degrees with reference to the blue light sources 121 and 122.

In FIG. 36, the dichroic filter of the third dichroic mirror 126 has atransmission characteristic of reflecting light of a violet wavelengthrange less than approximately 430 nm and passing light of a blue, greenand red wavelength range more than the same. The third dichroic mirror126 passes the first blue light LB1 from the first blue light source 121through the collimator lens 75, and reflects the second blue light LB2from the second blue light source 122 through the collimator lens 125.Thus, light paths of the blue light LB1 and LB2 are coupled together. InFIG. 20, the second dichroic mirror 80 has a transmission characteristicof reflecting light of a blue wavelength range less than approximately460 nm. Thus, the second blue light LB2 reflected by the third dichroicmirror 126 is reflected by the second dichroic mirror 80 and directed tothe condenser lens 82. Consequently, all of the light paths of the bluelight LB1 and LB2, green fluorescence LGf and red light LR are coupledtogether.

The absorption coefficient μa of hemoglobin in blood comes to the peakat approximately 405 nm, as has been described with FIG. 9. Lightapplied to an object of interest has a small depth of penetrationaccording to smallness of the wavelength. See FIG. 10. The first bluelight LB1 from the first blue light source 121 with the centralwavelength of 460 plus or minus 10 nm has a relatively large depth ofpenetration with a relatively large wavelength, and is absorbed inmucosal blood vessels (medium deep) disposed at a lamina propria of themucosa more than in surface blood vessels as a target of the aboveembodiment. Thus, the first blue light LB1 is used as special light forenhancement of the mucosal blood vessels. In contrast, the second bluelight LB2 from the second blue light source 122 with the centralwavelength of 405 plus or minus 10 nm has a relatively small depth ofpenetration with a relatively small wavelength, and is absorbed insubsurface blood vessels disposed at an epithelium (mucosa surface).Thus, the second blue light LB2 is used as special light for enhancementof the subsurface blood vessels. The blue light sources 121 and 122 areswitched on and off selectively to use the blue light LB1 and LB2, sothat a vessel enhancement image can be obtained with high contrast ofthe mucosal blood vessels or the subsurface blood vessels.

In FIG. 37, the green and red light sources 36 and 37 and the first bluelight source 121 in the normal imaging mode are turned on according to atime point of the storing of the image sensor 56, to apply theillumination light LW2 (LB1+LGf+LR) to an object of interest, theillumination light LW2 being mixture of the first blue light LB1, greenfluorescence LGf and red light LR. In FIG. 38, the green light source 36and the first blue light source 121 in the vessel enhancement imaging ofmucosal blood vessels (medium deep) are turned on according to a timepoint of the storing of the image sensor 56, to apply the illuminationlight LW3 (LB1+LGf) to an object of interest, the illumination light LW3being mixture of the first blue light LB1 and green fluorescence LGf. InFIG. 39, the green light source 36 and the second blue light source 122in the vessel enhancement imaging of subsurface blood vessels are turnedon according to a time point of the storing of the image sensor 56, toapply the illumination light LW4 (LB2+LGf) to an object of interest, theillumination light LW4 being mixture of the second blue light LB2 andgreen fluorescence LGf.

Each component of the light LW2-LW4 is separated by the micro colorfilters in the image sensor 56. Reflected light corresponding to theblue light LB1 and LB2 is mainly received by the B pixels. Reflectedlight corresponding to the green fluorescence LGf is mainly received bythe G pixels. Reflected light corresponding to the red light LR ismainly received by the R pixels. The image sensor 56 sequentiallyoutputs the image signals B, G and R at the frame rate according to atime point of the readout.

The image signal B contains a component of reflected light correspondingto the first or second blue light LB1 or LB2, so that mucosal bloodvessels (medium deep) or subsurface blood vessels can be expressed withhigh contrast. In a manner similar to surface blood vessels, vesseldensity between the mucosal blood vessels or subsurface blood vessels islikely to be higher in a lesion of a cancer or the like than that innormal body tissue. Thus, the feature of the light source apparatus 120in the embodiment is effective in clearly expressing the mucosal bloodvessels or subsurface blood vessels with a specifically patterned formin the mucosal blood vessels or subsurface blood vessels.

In the above embodiments, the peak wavelengths of blue light are 430,405 and 460 nm. However, a peak wavelength of blue light from a bluelight source can be 415 nm.

Especially, the wavelengths 405, 415 and 430 nm are characterized inthat the absorption coefficient μa of hemoglobin in blood is high in theabsorption spectrum of the hemoglobin in blood in FIG. 9. Therefore, avessel enhancement image can be obtained with enhanced contrast betweenblood vessels and other tissue. Should a balance of the spectrum oflight for the vessel enhancement imaging be lost in use of the blueexcitation light LBe from the green light source 36, serious influenceoccurs to the imaging due to changes in color balance of the vesselenhancement image.

It follows that cutting off the blue excitation light LBe from the greenlight source 36 with the excitation light cut-off filter (wavelengthcut-off filter component) is effective typically in case a peakwavelength of blue light from a blue light source is one of 405, 415 and430 nm.

In FIG. 40, a transmission characteristic of another example isillustrated. The wavelength cut-off filter 97 of the third embodiment orthe wavelength cut-off filter 117 of the fourth embodiment can have thetransmission characteristic as depicted. This is a narrow band filter ofgreen with a band pass characteristic of reflecting light of a green andred wavelength range equal to or more than approximately 550 nm andlight of a green and blue wavelength range less than approximately 530nm, and passing other light of a green wavelength range. The excitationlight cut-off filter of this transmission characteristic can cut off theblue excitation light LBe and obtain light of a wavelength range of530-550 nm included in the green fluorescence LGf, so that contrast ofsubsurface or deep blood vessels in the display image can be enhanced.

To this end, a filter moving mechanism is disposed for moving theexcitation light cut-off filter between an active position in a lightpath of the green light source 36 and an inactive position set out ofthe light path of the green light source 36. In the normal imaging mode,the excitation light cut-off filter is shifted to the inactive position.In the vessel enhancement imaging mode, the excitation light cut-offfilter is shifted to the active position.

The mounting method of the LEDs in the invention is not limited to thefirst embodiment. For example, a micro lens can be disposed on an exitsurface of the resin encapsulant 35 c or the green emitting phosphor 47in FIGS. 4 and 5 for adjusting an angle of divergence. Also, a housingof a bullet shape including a micro lens can be used for containing anLED in place of the surface mounting type. In the above embodiments, thegreen emitting phosphor 47 and the blue excitation light source device44 are both mounted on the semiconductor substrate 36 a by way of thegreen light source 36. However, the green emitting phosphor 47 can beseparate from the semiconductor substrate 36 a. To this end, guidingoptics such as a lens or fiber optics can be added between the blueexcitation light source device 44 and the green emitting phosphor 47, toguide excitation light from the blue excitation light source device 44to the green emitting phosphor 47.

Sixth Preferred Embodiment

In FIG. 41, another preferred light source apparatus includes a blueexcitation light source device or light source LD 131 (light sourcelaser diode), in place of the LED. A fluorescent type of green lightsource 130 of a semiconductor includes the light source LD 131 and greenemitting phosphor 132 disposed downstream of the light source LD 131.The green light source 130 is used in place of the green light source 36of the above embodiments.

For this purpose, a transparent rotatable disk 133 is prepared. Acoating is applied to a surface of the rotatable disk 133 to form thegreen emitting phosphor 132. A rotating mechanism 134 with a motor andthe like rotates the rotatable disk 133. Blue excitation light from thelight source LD 131 is applied to a point that is disposed eccentricallyon the rotatable disk 133. Rotation of the rotatable disk 133 canprevent the excitation light from concentrating at one point on thegreen emitting phosphor 132. Should excitation light concentrate at onepoint on the green emitting phosphor 132, the point of the greenemitting phosphor 132 will be overheated to quicken degradation of thegreen emitting phosphor 132. However, the feature of the embodiment canprevent such a difficulty. Note that a condenser lens 135 condenses theblue excitation light from the light source LD 131 on the rotatable disk133.

Also, an excitation light cut-off filter (wavelength cut-off filtercomponent) may be formed on an exit surface of the rotatable disk 133.It is possible to use an organic electro luminescence device (EL device)and the like may be used instead of the LEDs and LDs. Furthermore, theblue and red light sources 35 and 37 and the like other than the lightsource of a type with green emitting phosphor can be constituted by anLD, organic EL device and the like.

The excitation light cut-off filter for cutting all of the excitationlight is used in the above embodiments. However, the invention is notlimited to those embodiments. An excitation light cut-off filter(wavelength cut-off filter component) according to the invention can bean element with a transmission characteristic for reducing a lightamount of the excitation light, for example, reducing the light amountby 50%. However, it is desirable for an excitation light cut-off filterto cut off 100% of the excitation light because of high effect.

The path coupler of the invention is not limited to the aboveembodiments. It is possible to use a dichroic prism including a prismand a dichroic filter formed thereon in place of the dichroic mirror.For the purpose of coupling the light paths, it is possible to use alight guide device of a branch form having plural entrance ends forlight sources and one exit end directed to the entrance end of the lightguide device of the endoscope, in place of the optics having thedichroic filter. The light guide device of the branch form is a fiberbundle of plural optical fibers. Proximal ends of the optical fibers aregrouped at a predetermined number of fibers to form the plural entranceends. Light sources of a semiconductor are disposed upstream ofrespectively the entrance ends. An excitation light cut-off filter isdisposed between the fluorescent type of green light source and one ofthe entrance ends.

In the above embodiments, the image sensor is the color image sensor.However, an image sensor in an endoscope system of the invention may bea monochromatic image sensor. In the above embodiment, the lightingcontrol is the simultaneous lighting (with normal white light), withwhich the color image sensor acquires image signals of B, G and Rsimultaneously. However, a lighting control in a light source apparatuscan be field sequential lighting, in which blue, green and red lightcomponents are applied to an object of interest one after another, for amonochromatic image sensor to acquire image signals of B, G and Rsequentially.

In FIG. 42, the field sequential lighting is illustrated. In the vesselenhancement imaging mode, the blue and green light sources 35 and 36 areturned on and off alternately according to time points of the storing ofthe image sensor. The blue light LB and the green fluorescence LGf areapplied to an object of interest alternately. The image processorproduces a vessel enhancement image of one frame according to imagesignals of two consecutive frames.

Furthermore, the lighting control in the endoscope system can bechangeable between simultaneous lighting and field sequential lighting.In FIG. 15, the simultaneous lighting is set for emitting the mixedillumination light LW1 of the blue light LB and the green fluorescenceLGf. In FIG. 42, the field sequential lighting is set for sequentiallyemitting the blue light LB and the green fluorescence LGf. It ispossible to utilize advantages of both the simultaneous lighting and thefield sequential lighting.

Furthermore, the features of the various embodiments can be combinedwith one another according to the present invention.

Furthermore, a light source apparatus with the feature of the inventioncan be a light source apparatus including a violet semiconductor lightsource (violet LED). In the above embodiments, the wavelength range ofthe blue light LB from the blue LED 43 overlaps on that of the blueexcitation light LBe from the blue excitation light source device 44.Similarly, a wavelength range of violet light from the violetsemiconductor light source is likely to overlap partially on that of theblue excitation light LBe from the blue excitation light source device44. However, the feature of the invention is effective in preventinginfluence of the blue excitation light LBe to a light amount of theviolet light.

In the above embodiments, the light source apparatus 13 is separate fromthe processing apparatus 12. However, a composite apparatus includingcomponents of the processing apparatus 12 and the light source apparatus13 may be used in the invention. Furthermore, an endoscope and lightsource apparatus of the invention can be used with a fiber scope forguiding reflected light from an object of interest by use of an imageguide, an ultrasonic endoscope including an image sensor and anultrasonic transducer incorporated in the tip device.

According one embodiment mode of the invention, furthermore, a redsemiconductor light source emits red light of a red wavelength range.

According another embodiment mode of the invention, the bluesemiconductor light source emits the blue light with a peak wavelengthof at least one of 405, 415, 430 and 460 nm.

According still another embodiment mode of the invention, the blueexcitation light source device is a light emitting diode.

Although the present invention has been fully described by way of thepreferred embodiments thereof with reference to the accompanyingdrawings, various changes and modifications will be apparent to thosehaving skill in this field. Therefore, unless otherwise these changesand modifications depart from the scope of the present invention, theyshould be construed as included therein.

What is claimed is:
 1. A light source apparatus for supplying a light guide device of an endoscope with light, comprising: a blue semiconductor light source for emitting blue light of a blue wavelength range; a fluorescent type of a green semiconductor light source, having a blue excitation light source device and green emitting phosphor, said blue excitation light source device emitting blue excitation light of a violet to blue wavelength range overlapping on said blue wavelength range of said blue light, said green emitting phosphor being excited by said blue excitation light for emitting green fluorescence of a green wavelength range; a wavelength cut-off filter component, disposed between said blue excitation light source device and said light guide device, for cutting off said blue excitation light.
 2. A light source apparatus as defined in claim 1, further comprising a path coupler for coupling two light paths from said blue and green semiconductor light sources together.
 3. A light source apparatus as defined in claim 2, wherein said wavelength cut-off filter component is disposed on said path coupler, or disposed between said path coupler and said green semiconductor light source.
 4. A light source apparatus as defined in claim 2, wherein said path coupler includes optics disposed at an intersection point between said two light paths; said wavelength cut-off filter component is a dichroic filter formed on said optics.
 5. A light source apparatus as defined in claim 1, further comprising a driver for simultaneously driving said blue and green semiconductor light sources for vessel enhancement imaging, to output mixed light of said blue light and said green fluorescence.
 6. A light source apparatus as defined in claim 1, further comprising a driver for alternately driving said blue and green semiconductor light sources for vessel enhancement imaging, sequentially to output said blue light and said green fluorescence.
 7. Alight source apparatus as defined in claim 1, further comprising a driver, connected to said blue and green semiconductor light sources, and changeable between simultaneous lighting and field sequential lighting; wherein in said simultaneous lighting, said driver simultaneously drives said blue and green semiconductor light sources for vessel enhancement imaging, to output mixed light of said blue light and said green fluorescence; in said field sequential lighting, said driver alternately drives said blue and green semiconductor light sources for vessel enhancement imaging, sequentially to output said blue light and said green fluorescence.
 8. Alight source apparatus as defined in claim. 1, wherein said blue semiconductor light source emits said blue light with a peak wavelength of at least one of 405, 415, 430 and 460 nm.
 9. Alight source apparatus as defined in claim. 1, further comprising: a measurement sensor for measuring a light amount of said blue light or said green fluorescence emitted by at least one of said blue and green semiconductor light sources; an optical path device for guiding part of said blue light or said green fluorescence to said measurement sensor; a light source controller for controlling power supplied to said blue or green semiconductor light source according to a measurement result of said measurement sensor.
 10. Alight source apparatus as defined in claim 9, wherein said measurement sensor and said optical path device are associated with said green semiconductor light source, and said light source controller adjusts said power supplied to said blue excitation light source device according to said measurement result.
 11. A light source apparatus as defined in claim 9, further comprising a band pass filter, disposed upstream of said measurement sensor, for receiving light emitted by said green semiconductor light source and reflected by said optical path device, and cutting off light with a wavelength different from said green wavelength range of said green fluorescence.
 12. A light source apparatus as defined in claim 9, wherein said wavelength cut-off filter component is a wavelength cut-off filter of a plate shape disposed between said green semiconductor light source and said optical path device.
 13. A light source apparatus as defined in claim 9, wherein said optical path device includes a transparent glass plate, disposed downstream of said blue or green semiconductor light source, for reflecting said part of said blue light or said green fluorescence by Fresnel reflection, to guide said part to said sensor.
 14. A light source apparatus as defined in claim 1, further comprising a rotatable disk having said green emitting phosphor formed on a surface thereof; wherein said blue excitation light source device emits said blue excitation light toward said rotatable disk being rotated at an eccentric point thereof.
 15. An endoscope system including an endoscope having a light guide device for guiding light, and a light source apparatus for supplying said light guide device with said light, said endoscope system comprising: said light source apparatus including: a blue semiconductor light source for emitting blue light of a blue wavelength range; a fluorescent type of a green semiconductor light source, having a blue excitation light source device and green emitting phosphor, said blue excitation light source device emitting blue excitation light of a violet to blue wavelength range overlapping on said blue wavelength range of said blue light, said green emitting phosphor being excited by said blue excitation light for emitting green fluorescence of a green wavelength range; a wavelength cut-off filter component, disposed between said blue excitation light source device and said light guide device, for cutting off said blue excitation light. 